Neurexins are neuronal cell surface proteins involved in neuron-neuron recognition and adhesion, critical in establishing our neural network. Neurexin-1-_ is comprised of a single domain with no sequence homology to any protein with known structure. Diffraction is poor extending currently to 7 E in house, but using 10 minute exposures at SSRL 9-1 a 3 E native data set has been collected. A promising Pt derivative has been identified using only a partial data set. We plan to collect a complete data set of our Pt derivatized N-1-_ crystals. In addition, because the poor diffraction of our crystals limits what can be done at home, we plan to screen additional heavy atom derivatives. A detailed procedure has been worked out to rapidly screen a large number of crystals. Complete data sets will only be collected if isomorphous (and anomalous) differences can be demonstrated at the beam line. The presence of non-crystallographic symmetry in our crystals makes even low resolution phases extremely valuable for the structure determination.